Prezentace aplikace PowerPoint

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SO42 ATP 8 e 8 H S2 4 H2O AMP
PPi
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APS sulfotransferase, using APS as a sulfuryl
donor, transfers sulfate to an acceptor thiol
compound, possibly glutathione. The resulting
organic thiosulfonate is reduced to thiosulfide
by a ferredoxin-dependent thiosulfonate reductase.
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APS is first phosphorylated to PAPS by APS
kinase. PAPS reductase then produces sulfite by
using electrons donated from thioredoxin. Sulfite
reductase then completes the reduction to sulfide
by using electrons from ferredoxin.
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major endproduct of the reductive sulfate
assimilation, glutathione, is the major
nonprotein thiol in plants (its milimolar
concentrations far exceed the micromolar conc. of
cysteine)
involved in the storage and long distance
transport of reduced sulfur, in signal
transduction pathways, in scavenging active
oxygen species, in detoxifying xenobiotics and
serving as a substrate for phytochelatin synthesis
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Two phytochelatin molecules (gama-Glu-Cys)2Gly
coordinated with an ion of cadmium. By binding
toxic heavy metal ions, phytochelatins remove
them from the cellular machinery.
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(A) The phytoplankton-climate connection.
Phytoplankton-produced DMSP (dimethylsulfoniopropi
onate) is broken down by bacteria to DMS
(dimethyl sulfide) and acrylate. DMS volatilizes
and is oxidized to DMSO and to sulfate, which
nucleates water droplets, leading to cloud
formation.
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